Hydraulic Fluid Compositions

ABSTRACT

An aqueous hydraulic fluid composition comprising a first lubricant comprising at least one phospholipid and a second lubricant comprising an alkoxylate salt. The aqueous hydraulic fluid composition contains less than about 20% by weight (preferably none or substantially none) of an oil selected from the group consisting of mineral oils, synthetic hydrocarbon oils, and mixtures thereof. The use of alkoxylate salts provides increased lubricity and also acts as an emulsion stabilizer for the composition.

FIELD OF THE INVENTION

This invention relates to aqueous hydraulic fluid compositions,especially hydraulic fluid compositions that are suitable for use inblowout preventer devices used to control wellhead pressure of oilwells.

BACKGROUND OF THE INVENTION

Hydraulic fluids are low viscosity fluids used for the transmission ofuseful power by the flow of the fluid under pressure from a power sourceto a load. A liquid hydraulic fluid generally transmits power by virtueof its displacement under a state of stress. Hydraulic fluids generallyalso lower the coefficient of friction. To be effective, thecompositions typically have sufficient antiwear, antiweld, and extremepressure properties to minimize metal damage from metal-to-metal contactunder high load conditions.

Hydraulic fluids are usable in blowout preventer (BOP) devices which areused to control well-head pressure of an oil well that is being drilledand/or in marine environments such as in off-shore oil drilling rigs. A“blowout” is defined herein as an uncontrolled flow of gas, oil, orother well fluids into the atmosphere or into an underground formation.A blowout for gusher) can occur when formation pressure exceeds thepressure applied to it by the drilling or extraction apparatus. Thus, a“blowout preventer” is one of several valves installed at the wellheadto prevent the escape of pressure either in the annular space betweenthe casing and drill pipe or in open hole (i.e., hole with no drillpipe) during drilling completion operations. The blowout preventer is ahydraulic device that forms a virtually instantaneously seal around thedrill string to seal off well-head pressure when an area of highpressure such as a high pressure gas pocket has been contacted. BOP's onland rigs are typically located beneath the rig at the land's surface;on jackup or platform rigs, are located at the water's surface; and onfloating offshore rigs, are located on the seafloor. A BOP control unitstores hydraulic fluid under pressure and provides a mechanism foropening and closing the BOP's quickly and reliably. The opening andclosing forces in the unit are typically provided by compressed air andhydraulic pressure.

There are many reported problems associated with conventional hydraulicfluids used in BOP applications. For example, the handling of manyconventional hydraulic fluids may be complicated by theircombustibility, i.e., low flash points, and poor fire resistance. Inaddition, many conventional hydraulic fluids are toxic and accidentalspillage, especially into the ocean, creates significant environmentalproblems.

Many conventional hydraulic fluids are not suitable for BOP applicationsdue to their low tolerance to sea water contamination or tocontamination by hydrocarbons, i.e., they tend to readily form emulsionswith small amounts of hydrocarbons. Furthermore, in marine environments,problems arise due to the lack of biodegradability of the hydraulicfluid and to bacterial infestations arising in the hydraulic fluid,especially from anaerobic bacteria such as the sulfate reducing bacteriaprevalent in sea water.

Other problems associated with the use of conventional hydraulic fluidsunder the extreme conditions encountered in BOP devices include: (1)some conventional hydraulic fluids may, cause corrosion with metals incontact with the fluid; (2) some conventional hydraulic fluids arereactive with paints or other metal coatings or tend to react withelastomeric substances or at least cause swelling of the elastomericsubstance; (3) poor longterm stability, especially at elevatedtemperatures; (4) some hydraulic fluids require anti-oxidants to avoidthe oxidation of contained components; (5) some hydraulic fluids are notreadily concentrated for ease in shipping; and (6) many conventionalhydraulic fluids have a non-neutral pH, thereby enhancing theopportunity for reaction with materials in contact with it. For all ofthese reasons, it has become advantageous to use aqueous hydraulicfluids in BOP applications and various aqueous formulations have beendeveloped that are usable in such applications.

In addition, the demand for aqueous based hydraulic fluid compositionssuch as may be used in BOP devices continues to increase due to theenvironmental, economic and safety (e.g. high non-flammability)advantages of such fluids over conventional non-aqueous, oil-typehydraulic fluids.

The OSPAR Convention for the Protection of the Marine Environment of theNorth-East Atlantic, provides a list of substances used in preparationsused and discharged offshore which are considered to Pose Little or NoRisk to the Environment (PLONOR) which do not need to be heavilyregulated. Thus, it would be desirable to have an aqueous hydraulicfluid composition that is usable in BOP applications and containssubstantially only substances that are PLONOR approved.

An example of an aqueous hydraulic fluid composition that is usable inBOP devices is described in U.S. Patent Publication No. 2007/0078068 toAskew, the subject matter of which is herein incorporated by referencein its entirety. Askew describes an aqueous hydraulic fluid compositioncomprising at least one phospholipid lubricant which is preferably aplant-derived lecithin as the only lubricant in the composition and lessthan 20% by weight of a mineral oil, synthetic hydrocarbon oil ormixture thereof. Another example of an aqueous hydraulic fluidcomposition is described in U.S. Pat. No. 5,698,498 to Luciani et al.,the subject matter of which is herein incorporated by reference in itsentirety.

The inventor of the present invention has identified additionaladditives that can provide improved lubricity and improved stability ofaqueous hydraulic fluid compositions that are usable under the extremeconditions encountered in BOP devices.

To that end, the inventor of the present invention has determined thatthe use of a stearate such as calcium stearate provides improvedlubricity of the aqueous hydraulic fluid composition. The use of calciumstearate in the composition also provides significantly increasedstability of the composition. Calcium stearate is also on the PLONORlist of acceptable substances.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved aqueoushydraulic fluid composition for use under the extreme conditionsencountered in BOP devices.

It is another object of the present invention to provide an aqueoushydraulic fluid composition that exhibits improved lubricity.

It is still another object of the present invention to provide anaqueous hydraulic fluid concentrate that has greater stability, in bothits concentrated and diluted form.

It is still another object of the present invention to provide ahydraulic fluid composition that contains materials on the PLONOR listof acceptable substances.

To that end, the present invention relates to an improved aqueoushydraulic fluid composition comprising:

a first lubricant comprising at least one phospholipid; and

a second lubricant comprising an alkoxylate salt, preferably one or moresalts of alkoxylates selected from the group consisting of laurates,palmitates, oleates, and stearates;

wherein the hydraulic fluid composition comprises less than about 20% byweight (preferably none or substantially none) of an oil selected fromthe group consisting of mineral oils, synthetic hydrocarbon oils, andmixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a graph of a Falex extreme pressure test performed onvarious formulations containing lecithin alone or in combination withcalcium stearate.

FIG. 2 depicts a graph of a Falex extreme pressure test performed onaqueous formulations containing 8% by weight lecithin after dilution to10% w/w with water.

FIG. 3 depicts a graph of a Falex extreme pressure test performed onformulations containing 4% w/w lecithin after dilution to 10% wily withwater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The inventor of the present invention has discovered that the additionof a second lubricant comprising an alkoxylate salt to an aqueoushydraulic fluid composition containing a phospholipid as a firstlubricant, improves the lubricity of the hydraulic fluid composition andalso increases the stability of the composition, in both itsconcentrated state. The use of alkoxylate salts to stabilize PLONORhydraulic fluid compositions has not previously been contemplated.

Suitable alkoxylate salts include salts of alkoxylates with from 2 to 30carbons in the alkoxylate carbon chain (straight or branched).Preferable alkoxylate salts include alkali metal, alkaline earth andammonium salts of (preferably calcium, magnesium and zinc salts of)laurates, palmitates, oleates and stearates, such as calcium stearate,magnesium stearate and zinc stearate. Calcium stearate is most preferredsince it is on the PLONOR list.

To that end, in one embodiment, the present invent is directed to anaqueous hydraulic fluid composition comprising:

a first lubricant comprising at least one phospholipid; and

a second lubricant comprising a an alkoxylate salt;

wherein the hydraulic fluid composition comprises less than about 20% byweight (preferably none or substantially none) of an oil selected fromthe group consisting of mineral oils, synthetic hydrocarbon oils, andmixtures thereof.

Phospholipids usable in the formulations of the invention include anylipid containing a phosphoric acid derivative, such as lecithin orcephalin, preferably lecithin or derivatives thereof. Examples ofphospholipids include phosphatidylcholine, phosphatidylserine,phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid andmixtures thereof. The phospholipids may also be glycerophospholipids,more preferably, glycero derivatives of the above listed phospholipids.Typically, such glycerophospholipids have one or two acyl groups on aglycerol residue, and each acyl group contains a carbonyl and an alkylor alkenyl group. The alkyl or alkenyl groups generally contain fromabout 8 to about 30 carbon atoms, preferably 8 to about 25, mostpreferably 12 to about 24. Examples of these groups include octyl,dodecyl, hexadecyl, octadecyl, docosanyl, octenyl, dodecenyl,hexadecenyl and octadecenyl.

The acyl groups on the glycerophospholipids are generally derived fromfatty acids, which are acids having from about 8 to about 30 carbonatoms, preferably about 12 to about 24, most preferably about 12 toabout 18 carbon atoms. Examples of fatty acids include myristic,palmitic, stearic, oleic, linoleic, linolenic, arachidic, arachidonicacids, or mixtures thereof, preferably stearic, oleic, linoleic, andlinolenic acids or mixtures thereof.

Derivatives of phospholipids, including acylated or hydroxylatedphospholipids may also be used in the practice of the invention. Forinstance, lecithin as well as acylated and hydroxylated lecithin may beused in the present invention and may be prepared by methods known tothose skilled in the art.

Phospholipids may be prepared synthetically or derived from naturalsources. Synthetic phospholipids may be prepared by methods known tothose in the art. Naturally derived phospholipids are extracted byprocedures known to those in the art. Phospholipids may be derived fromanimal or vegetable sources. Animal sources include fish, fish oil,shellfish, bovine brain and any egg, especially chicken eggs. Vegetablesources include rapeseed, sunflower seed, peanut, palm kernel, cucurbitseed, wheat, barley, rice, olive, mango, avocado, palash, papaya,jangli, bodani, carrot, soybean, corn, and cottonseed. Phospholipids mayalso be derived from microorganisms, including blue-green algae, greenalgae, bacteria grown on methanol or methane and yeasts grown onalkanes. In a preferred embodiment, the phospholipids are derived fromvegetable sources, including soybean, corn, sunflower seed andcottonseed.

The present invention also contains an alkoxylate salt as a secondlubricant for the hydraulic fluid composition. The inventors of thepresent invention have determined that while phospholipids such aslecithin are good primary lubricants for use in aqueous hydraulic fluidcompositions, an improvement in lubricity is realized by adding analkoxylate salt (preferably a metal alkoxylate salt) to the compositionin an amount proportional to the concentration of phospholipid and inproportion to how much of the alkoxylate salt is solubilized by thesolution. This may be governed, at least in part, by the (phospholipid)to alkoxylate salt ratio. If too little phospholipid to alkoxylate isused, the alkoxylate salt may be precipitated out of solution ondilution of the formulation with water. In one embodiment, about 10%phospholipid is required to prevent precipitation of the alkoxylate saltin the formulation on dilution.

It is also known that PLONOR compositions can be very difficult tostabilize. The inventor of the present invention has surprisinglydiscovered that the addition of the alkoxylate salt to the hydraulicfluid composition stabilizes the fluid composition, which gives thefluid compositions a much longer shelf life. In addition, formulationscontaining lower levels of lecithin, such as motion compensation fluids,can also be stabilized with the alkoxylate salt of the invention. Whilecalcium stearate is the preferred alkoxylate salt for use incompositions of the invention, other alkoxylate salts including zincstearate and magnesium stearate are also usable in compositions of theinvention.

Because the alkoxylate salt, acts as a stabilizer for the hydraulicfluid composition, the need for an additional stabilizer in theformulation is eliminated. A typical PLONOR aqueous hydraulic fluidcompositions that contain a boron containing salt such as borax and/orinorganic phosphate salts in lecithin/monoethylene glycol concentratesare notoriously unstable and have a tendency to phase separate veryquickly especially in warm climates. Borax alone is also very difficultto stabilize in such formulations at the concentrations required. Theinventors of the present invention have determined that alkoxylatesalts, especially calcium stearate, act as an emulsion stabilizer aswell as a lubricant in these compositions. The use of calcium stearatein the composition stabilizes the composition and prevents thecomposition from phase separating over a much longer period of time.Thus, the use of calcium stearate in the aqueous hydraulic fluid of theinvention provides both a secondary lubricant and an emulsionstabilizer.

The aqueous hydraulic fluid compositions of the invention alsopreferably contain a biocide. The biocide is chosen so as to becompatible with the lubricating components, i.e., it does not affectlubricating properties. In one embodiment, a boron containing salt, suchas borax decahydrate, is used as the biocide. In another embodiment thebiocide may be a sulfur-containing biocide or a nitrogen-containingbiocide. Nitrogen-containing biocides include triazines, oxazolidines,and guanidines as well as compounds selected from fatty acid quaternaryammonium salts, such as didecyl dimethyl quaternary ammonium chloridesalt. Various biocides are described in U.S. Pat. No. 4,470,918 toMosier and U.S. Patent Publication No. US 2007/0078068 to Askew, thesubject matter of each of which is herein incorporated by reference inits entirety. The concentration of the biocide is sufficient to at leastsubstantially prevent bacterial growth in the hydraulic fluid andpreferably to kill the bacteria present.

The hydraulic fluid further comprises an antifreeze additive capable oflowering the freezing point of the hydraulic fluid to at least about−30° F., which is below the minimum temperature expected to beencountered in such environments. The antifreeze additive is chosen soas to be non-reactive with the lubricating components and biocide and istherefore not detrimental to the lubricating properties of the hydraulicfluid.

In one embodiment, the anti-freeze additive comprises at least onealcohol (preferably a dihydroxy alcohol) having from 2 to 4 carbon atomsin an amount sufficient to reduce the freezing point to below −30° F.Preferred alcohols include monoethylene glycol, glycerol, propyleneglycol, 2-butene-1,4-diol, polyethylene glycols or polypropyleneglycols. In one preferred embodiment, monoethylene glycol, which isPLONOR approved is used as the anti-freeze additive of the invention inan amount sufficient to reduce the freezing point of the hydraulic fluidcomposition to the desired temperature.

In a preferred embodiment, the hydraulic fluid composition of theinvention may also contain a corrosion inhibitor that prevents corrosionand oxidation. Examples of corrosion inhibitors include,inorganic/organic, phosphates, fatty carboxylic acids neutralized withan alkanolamine, amine carboxylates, alkylamines and alkanolamines aswell as copper corrosion inhibitors such as benzotriazoles. Suitablealkanolamines include monoethanolamine and triethanolamine. Suitablealkylamines comprise a C₆-C₂₀ linear or branched alkyl group. Suitablealkanolamines typically comprise 1 to 12 carbon atoms, and may comprisemore than one alkanol group, such as dialkanolamines andtrialkanolamines. Other corrosion inhibitors usable in the practice ofthe invention include water-soluble polyethoxylated fatty amines andpolyethoxylated diamines. The corrosion inhibitor is usable in aconcentration sufficient so that substantially no corrosion occurs,i.e., corrosion, if present, results in a loss of less than 10 micronsper year in the thickness of a metal in contact with the hydraulicfluid.

In addition, while the above-described embodiment is preferred forapplications such as in hydraulic fluid for blowout preventersencountered in or with offshore oil drilling rigs, other embodiments aresuitable for many applications. For example, in a substantiallycorrosion-free environment, a corrosion inhibitor need not be includedin the composition of the hydraulic fluid. Similarly, in an environmentin which bacterial infestation is not a problem, the biocide may beomitted. For applications at warm or elevated temperatures, afreezing-point depressant is not required.

In a particularly preferred embodiment, the hydraulic fluid is preparedas a concentrate which must be diluted with about 9 parts water or waterglycol mixture to about 1 part concentrate to achieve the workingconcentrations.

The present invention is further described by reference to the followingnon limiting examples:

Example 1

Formulations were prepared with lecithin in the concentrate and withoutcalcium stearate in a PLONOR formulation. A first formulation wasprepared with 7% by weight lecithin in the concentrate and no calciumstearate. A second formulation was prepared with 12% by weight lecithinand no calcium stearate. A third formulation was prepared with 14% byweight lecithin and no calcium stearate. A fourth formulation contained7% by weight lecithin and 7% by weight calcium stearate. In addition tothe above ingredients the PLONOR formulations contained:

Ingredient Weight % monoethylene glycol 62 inorganic phosphate salts 6water balance

Each formulation was diluted to 10% w/w with water and a Falex extremepressure (EP) test was performed on each fluid.

The Falex tester measures the torque experienced on a rotating test pinsubmerged in the test fluid, as it is subjected to increasing load. Theload on the pin is increased at 100 pound increments and the torquemeasured at each load increment.

The results were as follows:

TABLE 1 Comparison of various aqueous hydraulic fluid compositionsFormulation Maximum Applied Load Torque (concentration % by weight)(pounds) (in · Lbs) 7% lecithin 1400 69.0 12% lecithin 1800 52.1 14%lecithin 2500 44.0 7% lecithin and 7% calcium 2500 52.3 stearate

A graphical representation of this data is provided in FIG. 1. As isseen, the compositions containing 14% lecithin alone and 7% lecithinwith 7% calcium stearate provided the highest maximum applied load andthus the best extreme pressure performance.

Example 2

A first formulation was prepared with 8% by weight lecithin with 66% byweight monoethylene glycol (MEG) and water and a second formulation wasprepared with the addition of 1% calcium stearate to the firstformulation. An extreme pressure test was performed on each fluid andthe data are tabulated in Table 2. A graphical representation of thedata is provided in FIG. 2.

TABLE 2 Falex Extreme Pressure Test Data 8% lecithin with 8% lecithinwith MEG/water and 1% MEG/water calcium stearate Applied Load TorqueTorque (pounds) (in · Lbs) (in · Lbs) 300 7.1 3.3 400 7.6 5.1 500 9.46.2 600 11.4 6.9 700 13.9 8.1 800 18.5 10.5 900 22.0 14.5 1000 22.8 19.31100 23.4 21.4 1200 25.4 22.6 1300 28.3 24.0 1400 29.6 25.7 1500 30.527.3 1600 31.6 29.1 1700 33.0 31.1 1800 33.5 32.8 1900 34.9 34.6 200036.8 36.5

Example 3

A first formulation was prepared with 4% lecithin with 78% by weightmonoethylene glycol (MEG) and water and a second formulation wasprepared with the addition of 1% calcium stearate to the firstformulation. An extreme pressure test was performed on each fluid andthe data are tabulated in Table 3. A graphical representation of thedata is provided in FIG. 3.

TABLE 3 Falex Extreme Pressure Test Data 4% lecithin with 4% lecithinwith MEG/water and 1% MEG/water calcium stearate Applied Load TorqueTorque (pounds) (in · Lbs) (in · Lbs) 300 5.0 5.2 400 8.0 7.0 500 9.38.8 600 10.8 10.2 700 12.8 12.5 800 15.6 16.0 900 20.1 19.5 1000 25.521.0 1100 25.6 21.5 1200 26.5 23.1 1300 27.9 25.6 1400 29.6 27.5 150031.0 29.0 1600 32.7 30.7 1700 34.6 32.9 1800 35.8 34.8 1900 37.3 35.22000 38.8 35.0 2100 40.0 35.2 2200 41.2 35.1 2300 42.8 35.5 2400 43.835.4 2500 42.8 36.6

The above, examples demonstrate that the inventor of the presentinvention has determined that calcium stearate improves the lubricity ofthe formulation in every case.

It should also be understood that the following claims are intended tocover all of the generic and specific features of the inventiondescribed herein and all statements of the scope of the invention thatas a matter of language might fall there between.

1. (canceled)
 2. The aqueous hydraulic fluid composition according toclaim 15, wherein the composition comprises water in an amount betweenabout 10% and about 95% by weight based on the total weight of thehydraulic fluid composition.
 3. (canceled)
 4. (canceled)
 5. The aqueoushydraulic fluid composition according to claim 15, wherein thealkoxylate salt is selected from the group consisting of calciumstearate, zinc stearate and magnesium stearate.
 6. The aqueous hydraulicfluid composition according to claim 5, wherein the alkoxylate salt iscalcium stearate. 7-9. (canceled)
 10. The aqueous hydraulic fluidcomposition according to claim 15, wherein the composition comprises acorrosion inhibitor.
 11. The aqueous hydraulic fluid compositionaccording to claim 10, wherein the corrosion inhibitor is selected fromthe group consisting of inorganic phosphates, alkylcarboxylic acidsneutralized with an alkanolamine, alkylamines, alkanolamines, aminecarboxylates, and benzotriazoles.
 12. The aqueous hydraulic fluidcomposition according to claim 15, wherein the composition furthercomprises an anti-freeze additive.
 13. The aqueous hydraulic fluidcomposition according to claim 12, wherein the anti-freeze additive isselected from the group consisting of monoethylene glycol, glycerol,propylene glycol, 2-butene-1,4-diol, polyethylene glycols andpolypropylene glycols.
 14. The aqueous hydraulic fluid compositionaccording to claim 13, wherein the anti-freeze additive is monoethyleneglycol.
 15. A hydraulic fluid composition comprising: a first lubricantcomprising a lecithin; and a second lubricant comprising a stearatesalt; and wherein the hydraulic fluid composition is at leastsubstantially free of an oil selected from the group consisting ofmineral oils, synthetic hydrocarbon oils, and mixtures thereof.
 16. Thehydraulic fluid composition according to claim 15, wherein hydraulicfluid composition is bio-degradable and, wherein substantially all ofthe ingredients in the hydraulic fluid composition are dischargable in amarine environment while posing little or no risk to the environment.17. The aqueous hydraulic fluid composition according to claim 15,wherein the composition further comprises a biocide, wherein the biocideis compatible with the first lubricant and the second lubricant suchthat the biocide does not affect the lubricating properties of thehydraulic fluid composition.
 18. The aqueous hydraulic fluid compositionaccording to claim 17, wherein the biocide is selected from the groupconsisting of boron containing salts, triazines, oxazolidines,guanidines, and fatty acid quaternary ammonium salts.
 19. The aqueoushydraulic fluid composition according to claim 18, wherein the biocideis borax decahydrate.
 20. The aqueous hydraulic fluid compositionaccording to claim 15, wherein the hydraulic fluid composition comprisesbetween about 4-14% of the lecithin and between about 1-7% of thealkoxylate salt.
 21. The aqueous hydraulic fluid composition accordingto claim 5, wherein the hydraulic fluid composition comprises betweenabout 1-7% of the alkoxylate salt.
 22. The aqueous hydraulic fluidcomposition according to claim 15, wherein the second lubricant is atleast substantially the only emulsion stabilizer in the hydraulic fluidcomposition.
 23. A method of making a hydraulic fluid composition thatis usable in a marine environment, the method comprising the steps of a)preparing a hydraulic fluid concentrate comprising: i) a first lubricantcomprising a lecithin; ii) a second lubricant comprising an alkoxylatesalt; iii) optionally, a biocide; iv) optionally, a corrosion inhibitor;and v) optionally, an anti-freeze additive; and b) diluting thehydraulic fluid concentrate with water; wherein the hydraulic fluidcomposition is at least substantially free of an oil selected from thegroup consisting of mineral oils, synthetic hydrocarbon oils andmixtures thereof.
 24. The method according to claim 23, wherein thehydraulic fluid composition comprises water in an amount between about10% and about 95% by weight based on the total weight of the hydraulicfluid composition.
 25. The method according to claim 23, wherein thealkoxylate salt is selected from the group consisting of calciumstearate, zinc stearate and magnesium stearate.
 26. The method accordingto claim 25, wherein the alkoxylate salt is calcium stearate.
 27. Themethod according to claim 23, wherein the hydraulic fluid concentratecomprises a corrosion inhibitor and the corrosion inhibitor is selectedfrom the group consisting of inorganic phosphates, alkylcarboxylic acidsneutralized with an alkanolamine, alkylamines, alkanolamines, aminecarboxylates, and benzotriazoles.
 28. The method according to claim 23,wherein the hydraulic fluid concentrate comprises an anti-freezeadditive and the anti-freeze additive is selected from the groupconsisting of monoethylene glycol, glycerol, propylene glycol,2-butene-1,4-diol, polyethylene glycols and polypropylene glycols. 29.The method according to claim 28, wherein the anti-freeze additive ismonoethylene glycol.
 30. The method according to claim 23, whereinhydraulic fluid composition is bio-degradable and wherein substantiallyall of the ingredients in the hydraulic fluid composition aredischargable in a marine environment while posing little or no risk tothe environment.
 31. The method according to claim 23, wherein thehydraulic fluid concentrate comprises a biocide, wherein the biocide iscompatible with the first lubricant and the second lubricant such thatthe biocide does not affect the lubricating properties of the hydraulicfluid composition.
 32. The method according to claim 31, wherein thebiocide is selected from the group consisting of a boron containingsalt, triazines, oxazolidines, guanidines, and fatty acid quaternaryammonium salts.
 33. The method according to claim 32, wherein thebiocide is borax decahydrate.
 34. The method according to claim 23,wherein the hydraulic fluid composition comprises between about 4-14% ofthe lecithin and between about 1-7% of the alkoxylate salt.
 35. Themethod according to claim 23, wherein the hydraulic fluid composition iscapable of generating a torque of at least 35 inch-pounds at an appliedload of at least 2400 pounds when the hydraulic fluid is subjected to aFalex extreme pressure test.
 36. The method according to claim 23,wherein the second lubricant is at least substantially the only emulsionstabilizer in the hydraulic fluid composition.